Weeds can invade the lawn over the winter, especially if there are strings of mild days that allow hardy weeds to overtake a dormant lawn. There are a few steps you can take in fall and early winter, before the ground freezes, that will help to prevent weed invasion in your lawn.

1. Mow Properly

A common fall mistake is to lower the lawnmower blade for the final mowing of the season. This scalps the lawn so that the grass blade length is not sufficient to shade out weed seed germination. It also weakens the grass, which makes it more likely that paths will be worn across the lawn during winter. Skip the blade lowering, or lower it so that the grass will be no less than 2 inches tall if you want to avoid this problem.

2. Aerate

Grass has more difficulty growing in compacted soil compared to many lawn weeds. After a summer of mowing, walking, and playing on the lawn, the soil can become quite compact. Bald spots can develop, which will only worsen over the winter months. Aerating removes plugs of soil and helps loosen up the compacted ground. Looser soil going into winter will also allow winter snow to melt and moisture to drain quickly, instead of causing a boggy lawn surface that drowns out grass.

3. Apply Herbicides

Some weeds are best treated in the fall. Crabgrass, for example, often begins to spring up in winter or very early spring when desired lawn grasses are still dormant. Applying a fall or early winter pre-emergent herbicide is the best strategy for killing crabgrass without damaging lawn grasses. Your lawn service can tailor the weed treatment to address the most common winter weeds in your area. 

4. Rake Thoroughly

Don't leave fallen leaves and tree debris sitting on the lawn going into winter. This debris will suffocate the grass beneath, leading to bare patches when you do finally rake it up come spring. Weeds will then quickly invade these bare patches since they tend to establish much more quickly than lawn grasses. If you don't want to toss the raked leaves, use them to mulch annual flower beds as the decomposing leaves will improve the soil.

5. Overseed 

For lawns that already have a few bare patches, late fall and early winter can be a good time to overseed so that grass grows in quickly to crown out potential weeds. The seed that is laid before the first snowfall will be protected from scavenging birds. As the weather begins to warm in a few months, these grass seeds will quickly germinate in the spring-moist soil.

Contact a lawn care service, such as Green Oasis, if you need more assistance with fall and early winter weed prevention.